Percussion cylinder device with pneu-matically cushioned back-stroke



1966 R. J. DESCHENES 3,232,130

PERCUSSION CYLINDER DEVICE WITH PNEUMATICALLY CUSHIONED BACK-STROKE Filed Jan. 23, 1964 INVENTOR. ROGER JOSEPH DESCHENES BYKWW- 774W United States Patent 2 Claims. (cl. 91-422) This invention relates generally to percussion equipment operated by compressed air, particularly that of the fixed or non-portable type which provides operations such as layout, riveting, stamping and hollow punchings.

This equipment is generally comprised of a pneumatic power unit of simple operation, the piston stem of which is firmly. secured to a percussion tool, and the cylinder of which is fixed on an arm movable along a column and cooperating with a stop means. This column and a work table placed under the percussion tool are supported by a framework. Furthermore, another arm, movable and lockable, can be provided on the column for guiding said tool.

In power units of this type, the piston is subjected on its upper face to the pressure acting in a chamber of the cylinder, and on its lower face to the action of a return spring,

the chamber being connected to a source of compressed airby means of a control valve, for example, as by means of a pedal. When compressed air is admitted into the aforementioned chamber, the action of the pressure against the upper face of the piston causes rapid displacement of this piston downward, resulting finally in a hammer blow of accumulated force on a tool against a work piece supported by the work table. When the compressed air contained in the cylinder escapes to the atmosphere by way of a distributing valve, the return spring placed under tension during the downward travel of the piston returns the piston and tool to their upper position of rest.

A percussion unit, such as above described, presents several disadvantages: principally, its embodiment is relatively large, and further, the expense of maintenance can be high by reason of the presence of a mechanical return gembodying a spring. Actually, the service conditions of this spring being placed under compression and released .in a forceful manner are particularly severe. The exacting characteristics for which the spring is calculated are -dilficult-to maintain and a breakage of the spring, which frequently occurs, is a'failure which results in the necessity of replacement of the damaged parts.

. The present invention overcomes the aforementioned inconveniences by elimin'atingthe spring and in replacing it by a pneumatic return means. By this means, a power unit of much smaller size may be utilized while at the 7 same time providing a pneumatic stopping effect which increases as a function of the work travel of the piston and tool, thus eliminating shock to the entire equipment.

In case of aspecific utilization of this power unit in a percussion device of the type considered, the movable L unit comprises an attaching stem extending into a single cylinder, this stem being'attached'to a piston separating the cylinder chamber into a direct operating chamber and a tubular a'ccumulatorchamber defined principally by said stem. .Further, the tubular accumulator chamber can be connected by ports provided in the attaching stem to an inter- 3,232,130 Patented Feb. 1, 1966 'to a support on a work table.

Several other characteristics of the invention will be apparent in the course of the detailed description which follows.

One embodiment of the object of the invention is shown in section in the single figure of the attached drawing.

In the drawing, the power unit comprises a cylinder body 1 comprising, for example, a metal tube having screw-threaded ends provided with a closing cup 2 at its upper end and shouldered guide ring 3 at the lower end. The cup and the ring are screw threaded and are fixed and locked with sealing tightness on the body 1.

A piston 4 is a slidably mounted in the cylinder with a piston stem 5 extending through and guided by the ring 3 and having a percussion tool 6 attached thereto by any appropriate means. The stem 5 constitutes not only a rigid connection of the piston to the tool but also an element defining a tubular accumulator chamber '7 and cooperates furthermore with the cylinder 1, the stop shoulder 8 of the ring 3 and lower annular face of said piston 9.

This piston 4 separates the tubular chamber 7 from a direct operating chamber 10 which it limits by its upper face 11 in cooperation with the cylinder 1 and the bottom of the cup 2.

The elfective surface of the upper face 11 of the piston is much greater than that of the lower face 9. Thus, when the chambers 9 and 10 are connected simultaneously to a source of compressed air, the force of the pressure acting in the upper chamber 10 is greater than that acting in the lower chamber 7 and causes the rapid descent of the mobile portion made up of piston 4, stem 5 and tool 6 in the direction of the arrow F. At the same time, the pres sure in the lower chamber 7 increases by reason of a retaining valve interposed between this chamber and the source. It can then be considered that said chamber 7 is an accumulator of pressure.

After the upper chamber 10 is connected to the free air, the pressure therein decreases progressively to atmospiston 4 and the stem 5 constitute a shouldered tube, the

upper end of which is sealed by a cup 15 covering a part of the operating face 11 of said piston. The connection of the tube to the cup 15 may be obtained by means of a screw thread. The lower end of the tube is closed by the percussion tool 6 which, being replaceable, is connected to said tube by any locking means, such as a tangential pin (not shown), and is sealed against leakage by an appropriate seal 16, such as a rubberring, for example.

The direct operating chamber 10 is connected by a pipe (not shown) through port 17 of the cup 2 to a control valve (not shown), whereby chamber 10 may be connected either to a source of compressed air orto the free air. The control valve may be controlled by a lever, a pedal, or otherwise. The aforementioned pipe may also connect said control valve. through a retaining valve or check valve, discussed below, to the accumulator chamber 7 communieating with the chamber .13.

In the embodiment shown, the direct acting chamber control valve, the accumulator of pressure 7 and 13. For this purpose, the cavity 13 communicates with chamber by a passageway 18 of the cup which supports the check valve 19. A power unit is thus providedwhich is very compact and the maintenance of which is reduced.

It is very evident that, if desired, the movable portion may comprise two pistons of different diameters, mounted slidably in two cylinders and defining two chambers connected to the control means and arranged such that they produce the same operational effect by the operating chamber acting on the large piston and the return accumulator chamber on the small piston. This particular construction of the power unit, though in accordance with the invention, presents the disadvantage of increasing the size and the cost of maintenance of said power unit.

In the present invention, it is readily seen that when the travel of the mobile portion increases, the pressure in the accumulator 7 and 13 increases also, thus providing a pneumatic cushioning which is a function increasing with the increase of travel.

In the embodiment shown, the sealing is provided by, first, between the chambers 7 and 10, and O-ring 20 of rubber, located in a groove of the piston 4 and bearing against the internal wall surface of the cylinder 1, and

further, between the chamber 7 and the exterior, by another O-ring seal of rubber 21 located in a groove in the ring 3 and disposed about the tubular stem 5.

The drawing shows that the ports 14 are located in rela tion to the lower face 9 of the piston 4 at a distance corresponding substantially at the minim m permissible height of the accumulator chamber 7, that is, when the piston 4 is necting of this cavity 7 and the direct-acting chamber 10 to the atmosphere. It then results that the descent of the movable unit is stopped when the pressure in said chamber 10 decreases and becomes substantially at atmosphere resulting in the return of this movable equipment toward the upper position, the upward movement being initiated when the action of the pressure in the accumulator chamber 7 becomes preponderant. The location of the ports 14 in relation to the lower face 9 of piston 4 determines the lower limit travel of the movable equipment.

The above-described apparatus relates to only one embodiment of the invention, it being understood that the application of the invention to the other realms of the industry is within theexpected skill of those versed in the art. In the above embodiment, the stem 5 of the piston may be attached to a percussion tool 6, and the cylinder body 1 may be supplied with means permitting adujstable attachment on a support column of a work table.

In accordance with another embodiment of the invention, the stem 5 may be solidly constructed, thus eliminating the chamber 13 and the check valve 19, in which event a separate pipe may be connected to chamber 7 through a port in the wall of body 1 to the control unit enabling simultaneous connection of chambers 7 and 10 to a source of pressurized fluid, with a retaining valve disposed in the pipe between chamber 7 and the control unit to maintain pressure within chamber 7 when the control unit is operated to exhaust chamber 10.

The invention is not limited to the form shown and described in detail because modifications may be made' without departing from its scope.

Having now described the invention, what I claim as new and desire to secure by Letters Patent, is:

1. A power cylinder, comprising: (a) a cylindrical body having a chamber therein and having end walls thereon, (b) a piston disposed in said chamber for reoiprocable movement therein and dividing said chamber into a first chamber on one side of said piston and a second chamber on the other side of said piston,

(c) hollow stern means connected to the other side of i said piston and slidably extending through one of said end walls for reciprocable movement with said piston, said stem having a slightly smaller diameter than that of said piston for reducing the effective face area of said other side of said piston with respect to the'said one-side of said piston,

((1) port means in said stem intercommunicating the interior thereof with said second chamber,

(e) said first and second chambers being adapted for connection to a source of fluid pressure whereby the simultaneous application of the same fluid pressure to both the first chamber and the second chamber initially provides a preponderant force on said one side of said piston to effect movement thereof and effecting a diminution of the size of the second chamber which provides an increase in force on said other side of said piston for effecting a cushioned stoppage of the piston movement, and

(f) check valve means for retaining fluid pressure in said second chamber when said first chamber is connected to exhaust whereby the piston is returned to its original position by the resultant preponderant pressure on said other side of said piston,

(g) said ports in said stem being spaced from said piston a predetermined distance whereby said ports pass through said one end wall for disposition externally of said cylindrical body to communicate the interior of said stem to atmosphere when the piston has moved to a predeterminedlimit within said cylindrical body.

2. A power cylinder, comprising:

(a) a cylindrical body having a chamber therein and having end wallsthereon,

(b) a piston disposed in said chamber for .reciprocable movement therein and dividing said chamber into a first chamber on one side of said piston and a second chamber on the other side of said piston,

(c) hollow stem means connected to the other side of said piston and slidably extending through one of said end walls for reciprocating movement with said piston, said stem having a slightly smaller diameter than that of said piston for reducing the effective face area of said other side of said piston with respect to the said one side of said piston,

(d) passage means intercommunicating said first chamber with said second chamber,

(e) valve means in said passage means providing unidirectional fluid fiow from said first chamber to said second chamber, I

(f) passage means for connecting'said first chamber to a source of fluid supply,

(g) port means in said stem intercomtnunicating the interior thereof with said"second chamber, said port means opening in the exterior wall of said stern a predetermined distance from said piston to extend through said one end wall for di'sposition 'exteriorly of said cylindrical body to communicate the "interior of said hollow stem with atmospherewhen the "piston has moved to a predetermined limitwithin said cylindrical body.

References Cited by the Examiner UNITED STATES PATENTS 2,746,425 5/1956 Schafer 91-422 X 3,160,075 12/1964 Powers 91----422 X FOREIGN PATENTS 1,017,411 9/1952 France.

SAMUEL LEVINE, Primary Examiner.

FRED E. ENGELTHALER, Examiner. 

1. A POWER CYLINDER, COMPRISING: (A) A CYLINDRICAL BODY HAVING A CHAMBER THEREIN AND HAVING END WALLS THEREON, (B) A PISTON DISPOSED IN SAID CHAMBER FOR RECIPROCABLE MOVEMENT THEREIN AND DIVIDING SAID CHAMBER INTO A FIRST CHAMBER ON ONE SIDE OF SAID PISTON AND A SECOND CHAMBER ON THE OTHER SIDE OF SAID PISTON, (C) HOLLOW STEM MEANS CONNECTED TO THE OTHER SIDE OF SAID PISTON AND SLIDABLY EXTENDING THROUGH ONE OF SAID END WALLS FOR RECIPROCABLE MOVEMENT WITH SAID PISTON, SAID STEM HAVING A SLIGHTLY SMALLER DIAMETER THAN THAT OF SAID PISTON FOR REDUCING THE EFFECTIVE FACE AREA OF SAID OTHER SIDE OF SAID PISTON WITH RESPECT TO THE SAID ONE SIDE OF SAID PISTON, (D) PORT MEANS IN SAID STEM INTERCOMMUNICATING THE INTERIOR THEREOF WITH SAID SECOND CHAMBER, (E) SAID FIRST AND SECOND CHAMBERS BEING ADAPTED FOR CONNECTION TO A SOURCE OF FLUID PRESSURE WHEREBY THE SIMULTANEOUS APPLICATION OF THE SAME FLUID PRESSURE TO BOTH THE FIRST CHAMBER AND THE SECOND CHAMBER INITIALLY PROVIDES A PREPONDERANT FORCE ON SAID ONE SIDE OF SAID PISTON TO EFFECT MOVEMENT THEREOF AND EFFECTING A DIMINUTION OF THE SIZE OF THE SECOND CHAMBER WHICH PROVIDES AN INCREASE IN FORCE ON SAID OTHER SIDE OF SAID PISTION FOR EFFECTING A CUSHIONED STOPPAGE OF THE PISTON MOVEMENT, AND (F) CHECK VALVE MEANS FOR RETAINING FLUID PRESSURE IN SAID SECOND CHAMBER WHEN SAID FIRST CHAMBER IS CONNECTED TO EXHAUST WHEREBY THE PISTON IS RETURNED TO ITS ORIGINAL POSITION BY THE RESULTANT PREPONDERANT PRESSURE ON SAID OTHER SIDE OF SAID PISTON, (G) SAID PORTS ON SAID STEM BEING SPACED FROM SAID PISTON A PREDETERMINED DISTANCE WHEREBY SAID PORTS PASS THROUGH SAID ONE END WALL FOR DISPOSITION EXTERNALLY OF SAID CYLINDRICAL BODY TO COMMUNICATE THE INTERIOR OF SAID STEM TO ATMOSPHERE WHEN THE PISTON HAS MOVED TO A PREDETERMINED LIMIT WITHIN SAID CYLINDRICAL BODY. 